1. Field
The present disclosure relates generally to automated systems and methods for positioning a tool relative to a workpiece for manufacturing or other purposes. More particularly, the present disclosure relates to controlling a positioning system comprising joint larger scale and smaller scale positioning mechanisms for positioning a tool in a work space.
2. Background
An automated positioning system may be used to perform a variety of manufacturing and other tasks. An automated positioning system may include a tool attached to a computer controlled positioning mechanism. The positioning mechanism may be configured to move the tool to various positions in a work space. For example, the positioning mechanism may be controlled to move the tool to various positions in the work space to perform various operations on a workpiece in the work space. A robotic arm is one example of a positioning mechanism that may be used in an automated positioning system.
For example, automated positioning systems are used in direct digital manufacturing. Direct digital manufacturing also may be referred to as additive manufacturing, additive free-form fabrication, solid free-form fabrication, rapid prototyping, layered manufacturing, or three-dimensional printing. Direct digital manufacturing machines may be used to produce three-dimensional solid objects from three-dimensional digital models of the objects. To produce an object, the direct digital manufacturing machine may lay down successive layers of liquid, powder, or sheet material corresponding to virtual cross sections from the digital model of the object. The layers are joined together or fused automatically to create the final object. Objects of almost any shape or having any geometric feature may be made using a direct digital manufacturing machine. A direct digital manufacturing machine also may be referred to as a three-dimensional printer.
Current direct digital manufacturing machines may have working volumes of approximately one cubic meter. It may be desirable to have direct digital manufacturing machines with larger working volumes to produce larger objects. For example, without limitation, it may be desirable to have direct digital manufacturing machines with working volumes of approximately ten cubic meters.
Efficiency of direct digital manufacturing processes may be improved if the nozzle or other tool for laying down material in a direct digital manufacturing machine may be moved throughout the working volume of the machine at relatively high speed and with relatively high acceleration. For example, without limitation, efficient direct digital manufacturing may be achieved with speeds of approximately 2 meters per second and accelerations of approximately 40 meters per second per second.
Larger volume versions of current direct digital manufacturing machine designs may require significantly stiffer and more massive linkages in the positioning mechanism to move the nozzle or other tool through the working volume at the higher speeds and accelerations desirable for efficiency. Larger motors may be required to move the larger linkages at the desired speeds and accelerations. As a result, such a machine may require more expensive components and may use more energy than current direct digital manufacturing machines.
Accordingly, it would be beneficial to have a method and apparatus that takes into account one or more of the issues discussed above as well as possibly other issues.